Nonvolatile memory architectures use materials exhibiting two or more stable states to retain stored information even in the absence of power. Each memory cell usually includes two electrodes and one or more materials between the electrodes; to change state, a voltage difference is created across the cell to induce current flow, with a first current flow “setting” a state and a second current flow “resetting” that state. Depending on architecture, the current flows used to change state can be made different, for example, different in magnitude or polarity (direction), or they can be the same.
Certain nonvolatile memory architectures use a “forming process,” to prepare a memory device for use. In a forming process, an initial, generally higher current flow (i.e., based on a voltage difference) is needed to help change state for the very first time, after which the operation of the device becomes relatively more consistent. The forming process is typically applied at the factory, at assembly, or at initial system configuration.
Such a forming process presents at least two disadvantages to memory devices, including that (a) it can be difficult or expensive in terms of silicon to generate or support a higher voltage associated with the forming process, and (b) the use of generally higher currents presents a risk of damaging memory cells and causing failure, through electric field damage or other forms of overload.
What is needed is an improved device or method that does not require a high forming voltage (or forming current). The present invention satisfies this need and provides further, related advantages.